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(#) Slots should be invoked in at most one place

!!! ERROR: Slots should be invoked in at most one place
   This is an error.

Id
:   `SlotReused`
Summary
:   Slots should be invoked in at most one place
Severity
:   Error
Category
:   Correctness
Platform
:   Any
Vendor
:   slack
Identifier
:   com.slack.lint.compose:compose-lints
Feedback
:   https://github.com/slackhq/compose-lints/issues
Min
:   Lint 8.7+
Compiled
:   Lint 8.7+
Artifact
:   [com.slack.lint.compose:compose-lint-checks](com_slack_lint_compose_compose-lint-checks.md.html)
Since
:   1.4.0
Affects
:   Kotlin and Java files and test sources
Editing
:   This check runs on the fly in the IDE editor
Implementation
:   [Source Code](https://github.com/slackhq/compose-lints/tree/main/compose-lint-checks/src/main/java/slack/lint/compose/SlotReusedDetector.kt)
Tests
:   [Source Code](https://github.com/slackhq/compose-lints/tree/main/compose-lint-checks/src/test/java/slack/lint/compose/SlotReusedDetectorTest.kt)
Copyright Year
:   2024

Slots should be invoked in at most once place to meet lifecycle
expectations. Slots should not be invoked in multiple places in source
code, where the invoking location changes based on some condition. This
will preserve the slot's internal state when the invoking location
changes. See
https://slackhq.github.io/compose-lints/rules/#do-not-invoke-slots-in-more-than-once-place
for more information.

(##) Example

Here is an example of lint warnings produced by this check:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~text
src/test.kt:7:Error: Slots should be invoked in at most once place to
meet lifecycle expectations. Slots should not be invoked in multiple
places in source code, where the invoking location changes based on some
condition. This will preserve the slot's internal state when the
invoking location changes. See
https://slackhq.github.io/compose-lints/rules/#do-not-invoke-slots-in-more-than-once-place
for more information. [SlotReused]
  slot: @Composable () -&gt; Unit,
  ----------------------------
src/test.kt:18:Error: Slots should be invoked in at most once place to
meet lifecycle expectations. Slots should not be invoked in multiple
places in source code, where the invoking location changes based on some
condition. This will preserve the slot's internal state when the
invoking location changes. See
https://slackhq.github.io/compose-lints/rules/#do-not-invoke-slots-in-more-than-once-place
for more information. [SlotReused]
  slot: @Composable () -&gt; Unit,
  ----------------------------
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Here is the source file referenced above:

`src/test.kt`:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~kotlin linenumbers
import androidx.compose.runtime.Composable
import androidx.compose.ui.Modifier

@Composable
fun Something(
  modifier: Modifier = Modifier,
  slot: @Composable () -> Unit,
) {
  Row(modifier) {
    slot()
    slot()
  }
}

@Composable
fun SomethingElse(
  modifier: Modifier = Modifier,
  slot: @Composable () -> Unit,
) {
  Column(modifier) {
    slot()
    Box {
      slot()
    }
  }
}
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

You can also visit the
[source code](https://github.com/slackhq/compose-lints/tree/main/compose-lint-checks/src/test/java/slack/lint/compose/SlotReusedDetectorTest.kt)
for the unit tests for this check to see additional scenarios.

The above example was automatically extracted from the first unit test
found for this lint check, `SlotReusedDetector.errors when the slot parameter of a Composable is used more than once at the same time`.
To report a problem with this extracted sample, visit
https://github.com/slackhq/compose-lints/issues.

(##) Including

!!!
   This is not a built-in check. To include it, add the below dependency
   to your project. This lint check is included in the lint documentation,
   but the Android team may or may not agree with its recommendations.

```
// build.gradle.kts
lintChecks("com.slack.lint.compose:compose-lint-checks:1.4.2")

// build.gradle
lintChecks 'com.slack.lint.compose:compose-lint-checks:1.4.2'

// build.gradle.kts with version catalogs:
lintChecks(libs.compose.lint.checks)

# libs.versions.toml
[versions]
compose-lint-checks = "1.4.2"
[libraries]
# For clarity and text wrapping purposes the following declaration is
# shown split up across lines, but in TOML it needs to be on a single
# line (see https://github.com/toml-lang/toml/issues/516) so adjust
# when pasting into libs.versions.toml:
compose-lint-checks = {
    module = "com.slack.lint.compose:compose-lint-checks",
    version.ref = "compose-lint-checks"
}
```

1.4.2 is the version this documentation was generated from;
there may be newer versions available.

[Additional details about com.slack.lint.compose:compose-lint-checks](com_slack_lint_compose_compose-lint-checks.md.html).
(##) Suppressing

You can suppress false positives using one of the following mechanisms:

* Using a suppression annotation like this on the enclosing
  element:

  ```kt
  // Kotlin
  @Suppress("SlotReused")
  fun method() {
     problematicStatement()
  }
  ```

  or

  ```java
  // Java
  @SuppressWarnings("SlotReused")
  void method() {
     problematicStatement();
  }
  ```

* Using a suppression comment like this on the line above:

  ```kt
  //noinspection SlotReused
  problematicStatement()
  ```

* Using a special `lint.xml` file in the source tree which turns off
  the check in that folder and any sub folder. A simple file might look
  like this:
  ```xml
  &lt;?xml version="1.0" encoding="UTF-8"?&gt;
  &lt;lint&gt;
      &lt;issue id="SlotReused" severity="ignore" /&gt;
  &lt;/lint&gt;
  ```
  Instead of `ignore` you can also change the severity here, for
  example from `error` to `warning`. You can find additional
  documentation on how to filter issues by path, regular expression and
  so on
  [here](https://googlesamples.github.io/android-custom-lint-rules/usage/lintxml.md.html).

* In Gradle projects, using the DSL syntax to configure lint. For
  example, you can use something like
  ```gradle
  lintOptions {
      disable 'SlotReused'
  }
  ```
  In Android projects this should be nested inside an `android { }`
  block.

* For manual invocations of `lint`, using the `--ignore` flag:
  ```
  $ lint --ignore SlotReused ...`
  ```

* Last, but not least, using baselines, as discussed
  [here](https://googlesamples.github.io/android-custom-lint-rules/usage/baselines.md.html).

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